1. Field of the Invention
The present invention generally relates to a transmission for an off-road vehicle, and more particularly to a transmission for an off-road vehicle that is cooled by ambient air.
2. Description of Related Art
Off-road vehicles are designed to be operated over rugged terrain. These vehicles are often operated on unpaved terrain such as, for example, steep inclines and declines, rough roads, and areas covered in mud and water.
The off-road vehicles typically include a frame that is supported by wheels. In one common arrangement, the vehicle has four wheels, i.e., a pair of front wheels and a pair of rear wheels. An internal combustion engine is employed to power at least the rear or front wheels, and most commonly, all of the wheels. Typically, the engine is combined with a transmission to form an engine unit. The transmission transfers power to an output shaft from a crankshaft of the engine. The output shaft drives the wheels through a drive mechanism. The off-road vehicle has a seat unit on which a driver and/or a passenger sit.
In some arrangements of conventional off-road vehicles, the transmission (e.g., a continuously variable transmission) includes an endless belt which links a variable pulley mechanism. A transmission case houses the belt and the pulley mechanism. Heat produced by friction occurs when the belt runs on the pulley mechanism and such heat can deteriorate the belt. In order to inhibit belt deterioration, the transmission can be provided with a cooling system that introduces air into the case and discharges the air to an external location outside of the case. See, for example, U.S. Pat. No. 5,086,858, which discloses an off-road vehicle that employs such a cooling system. The cooling system disclosed in U.S. Pat. No. 5,086,858, however, is susceptible to water intrusion under some operating conditions. Accordingly, in such an arrangement water can enter the case and can damage the belt and the pulley mechanism.